Centipede is a vertically oriented shoot ‘em up arcade game produced by Atari, Inc. in 1981. The game was designed by Ed Logg along with Dona Bailey, one of the few female game programmers in the industry at this time. It was also one of the first arcade coin-operated games to have a significant female player base, after Pac-Man. The player defends against centipedes, spiders, scorpions and fleas, completing a round after eliminating the centipede that winds down the playing field. The player is represented by a small, “somewhat humanoid head” at the bottom of the screen. The player moves the character about the bottom area of the screen with a trackball and fires laser shots at a centipede advancing from the top of the screen down through a field of mushrooms. Shooting any section of the centipede creates a mushroom; shooting one of the middle segments splits the centipede into two pieces at that point. Each piece then continues independently on its way down the board, with the first section of the rear piece becoming a new head. If the head is destroyed, the section behind it becomes the next head. The centipede starts at the top of the screen, traveling either left or right. When it hits a mushroom or the edge of the screen, it drops one level and switches direction. Thus, more mushrooms on the screen cause the centipede to descend more rapidly. The player can destroy mushrooms by shooting them, but each takes four hits to destroy. If the centipede reaches the bottom of the screen, it moves back and forth within the player area and one-segment “head” centipedes are periodically added. This continues until the player has eliminated both the original centipede and all heads. When all the centipede’s segments are destroyed, a new centipede forms at the top of the screen. Every time a centipede is eliminated, however, the next one is one segment shorter and is accompanied by one additional, fast-moving “head” centipede. A player loses a life when hit by a centipede or another enemy, such as a spider or a flea. The flea leaves mushrooms behind when fewer than five are in the player area, though the number required increases with level of difficulty. Spiders move across the player area in a zig-zag fashion and occasionally eat some of the mushrooms. Scorpions poison every mushroom they touch, but these never appear in the player’s movement region. A centipede touching a poisoned mushroom hurtles straight toward the player’s area. Upon reaching the player’s area, the centipede returns to normal behavior.

Missile Command is a 1980 arcade game by Atari, Inc. that was also licensed to Sega for European release. It is considered one of the most notable games from the Golden Age of Video Arcade Games. The plot of Missile Command is simple: the player’s six cities are being attacked by an endless hail of ballistic missiles, some of them even splitting like multiple independently targetable reentry vehicles (MIRVs), and in later levels smart bombs which can evade a less than perfectly targeted missile. As a regional commander of three anti-missile batteries, the player must defend six cities in their zone from being destroyed. The game is played by moving a crosshair across the sky background via a trackball and pressing one of three buttons to launch a counter-missile from the appropriate battery. Counter-missiles explode upon reaching the crosshair, leaving a fireball that persists for several seconds and destroys any enemy missiles that enter it. There are three batteries, each with ten missiles; a missile battery becomes useless when all its missiles are fired, or if the battery is destroyed by enemy fire. The missiles of the central battery fly to their targets at much greater speed; only these missiles can effectively kill a smart bomb at a distance. The game is staged as a series of levels of increasing difficulty; each level contains a set number of incoming enemy weapons. The weapons attack the six cities, as well as the missile batteries; being struck by an enemy weapon results in destruction of the city or missile battery. Enemy weapons are only able to destroy 3 cities during one level. A level ends if all the cities are destroyed, or when all enemy weaponry is destroyed or reaches its target. A player who runs out of missiles no longer has control over the remainder of the level. At the conclusion of a level, the player receives bonus points for any remaining cities or unused missiles. Between levels missile batteries are rebuilt and replenished; destroyed cities are rebuilt only at set point levels (usually 10 or 12K). The game inevitably ends when all six cities have been wiped out. Like most early arcade games, there is no way to “win” the game; the game just keeps going with ever faster and more prolific incoming missiles. The game, then, is just a contest in seeing how long the player can survive. On conclusion of the game, the screen displays “The End”, perhaps a poke at oncoming Nuclear Holocaust rather than the standard “Game Over” text (however, if the player is able to make the high score list, the game then prompts the player to enter his/her initials, with the “The End” sequence skipped). The game features an interesting bug: once a score of 810,000 is reached, a large number of cities are awarded (176 cities plus the continuing accrual of bonus cities) and it is possible to carry on playing for several hours. At some later stage the speed of missiles increases greatly for a few screens. On the 255th and 256th yellow screens, known as the 0x stages, the scoring increases by 256 times the base value. For good players these two 0x stages could earn over a million points. This enabled them to reach a score of approximately 2,800,000 (although only 6 digit scores were shown, so it would display 800,000) and at this point the accelerated rate would suddenly cease and the game would restart at its original (slow) speed and return to the first stage, but with the score and any saved cities retained. In this way it was possible to play this game for hours on end. Targeting crosshair: Aim your missiles quickly but carefully. Use the trackball to move the targeting crosshair to where you want the next missile to go, then press any Launch Control button to fire the missile. The missile will explode where the crosshair was positioned when the Launch Control button was pressed. Cities: There are six cities in total on the screen at one time, three on either side of the Delta Base. If one enemy missile or Smart Bomb manages to strike a city, that city will be wiped out. When all cities are destroyed, the game is over. Alpha Base: The missile base on the left side of the screen. Press the leftmost Launch Control button to launch an ABM from the Alpha Base. Delta Base: The missile base in the center of the screen. Press the middle Launch Control button to launch an ABM from the Delta Base. Omega Base: The missile base on the right side of the screen. Press the rightmost Launch Control button to launch an ABM from the Omega Base. NOTE: The Alpha and Omega Bases launch ABMs at a slower speed than the Delta Base, so you must plan further ahead when launching missiles from those bases. Defensive Missiles : The ABMs you launch to protect your cities. Each missile base contains 10 ABMs per wave. If any missile base is struck by an attack missile or smart bomb, the remaining stock of missiles for that wave are destroyed, and the missile base is rendered useless until the next wave. You receive bonus points for every ABM you have remaining at the end of each wave. Attack Missiles : Their only aim is to destroy your cities and missile bases. Every missile wave starts off with a hailstorm of attack missiles. They never deviate from their path. They may, however, turn into MIRVs. MIRV : Surprise! There is no warning when an attack missile turns into an MIRV (with multiple warheads). Think fast. Each new missile that the MIRV unleashes is carefully targeted. Killer Satellite: A mean-looking satellite that travels across the sky at a mid-level altitude and fires attack missiles. First appears in Wave 2. Bomber: A big slow-moving target that flies across the sky at a mid-level altitude, but watch out! It fires attack missiles. First appears in Wave 2. WARNING: If you destory a bomber or killer satellite before they deploy their missiles, you may see their missiles added to the downpour. An existing missile may also turn into an MIRV. Smart Bomb: Smart enough to avoid most explosion clouds from your ABMs. Your ABM must explode next to one in order to destroy it. You can also squeen it between two explosions to destroy it. First appears in Wave 5. ‘LOW’ Warning: As soon as there are only three ABMs left in a missile base, the game displays the word “LOW” underneath that base, and a warning signal sounds. Heed the warning.